1. Field of the Invention
The present invention relates to a device and method for allowing and/improving the injection of fuel assisted by compressed air or gas, or pneumatic injection, into an internal combustion engine comprising at least one pump crank case. The present invention is more especially applicable to a two stroke engine with air scavenging.
2. Description of the Prior Art
In the particular case of a two stroke engine with crank case scavenging during a considerable part of the air and fuel intake cycle, the transfer and exhaust ports are open simultaneously and a part of the air-fuel mixture admitted escapes to the atmosphere before the exhaust ports are closed, which results in a considerable reduction of the efficiency and considerable discharges of pollutants.
The injection of fuel assisted by air coming from the crank case overcomes this disadvantage. An example has been proposed by M. J. A. Culmann in the French patent FR No. 490.166. In this patent, scavenging of the cylinder takes place solely with the air coming from the pump crank case, another part of the air from the pump crank case is fed at a pressure close to the maximum pressure reached in this housing, into a sealed chamber which serves as compressed air source for supplying the pneumatic fuel injection device.
It has been discovered that such a device operated better when it was fed with compressed air at a pressure higher than that reigning in the pump crank case.
The prior art may be illustrated by the British patent No. GB-A-572.080, the German patent No. DE-C-833.885, the U.S. Pat. No. 31,902,701 and the French patent No. FRA-2 292 111.